Subsurface pests are difficult to control with pesticides since it is very hard to distribute the pesticides in the soil in a manner which assures a high degree of effectiveness. Attempts to inject liquid pesticide formations while plowing or otherwise turning soil have been of limited effectiveness because the pesticide does not get sufficiently uniformly distributed throughout the desired portion of the soil whereby the pests, e.g., nematodes, are not all contacted and killed in the areas which are skipped during treatment. Most liquids, namely those which do not easily vaporize, and which are interjected at intervals, simply cannot migrate horizontally, even in recently turned porous or moderately porous soil, in the way necessary to form the continuous barrier which is required to effectively alleviate damage by subsurface pests. The above problems have been increased due to the fact that many present day pesticides are somewhat less effective than previous pesticides which, unfortunately, have been discovered to have unacceptable environmental impacts. Thus, with many present day pesticides it is even more important that they be uniformly distributed throughout the soil. Similar problems exist with uniformity of distributing of other soil additives such as fertilizers and soil adjuvants with soil. Accordingly, there are disadvantages with subsurface injection of certain liquid soil additives.
U.S. Pat. No. 3,692,512 shows the preparation of foams for applying chemicals to plants, soil surfaces or the like in the open. The foam desirably is stable in the sense that it will stay moist on the plants surface for at least ten to fifteen minutes. U.S. Pat. No. 3,692,512 is, however, in no way concerned with deposition of pesticide from a foam delivery system and its distribution into the soil so as to control subsurface pests, alter soil properties, or the like.
The application of foamed pesticides to treat surfaces is also known. Copending application Ser. No. 08/063,361, filed May 17, 1993 and commonly assigned herewith, which is incorporated herein by reference, discloses the use of a wet foam with a specific degree of flowability for delivering pesticide dissolved or dispersed in the liquid carried by the wet foam to coat surfaces. It does not, however, disclose the use of foams for depositing and intermixing with soil to control subsurface crop pests or for fertilizer and/or soil adjuvant deposition and distribution into soil.
Another method which has been tried to control pests is via the generation of what is commonly referred to as a dry foam. Japanese patent publication SHO 58-43050, for example, shows the use of foams which include a termite pesticide, a foaming agent, an emulsifier and water. The foam is applied utilizing apparatus which is known to be used to chemically extinguish fires. Such an apparatus typically forms large volumes of foam in very short periods of time and the resulting foams have an expansion ratio, defined as the ratio of foam volume to volume of solution being foamed, of 100 to 1 or greater and substantially zero flowability in that the foams will disperse rather than flow. Further, the practical example set forth in the publication shows filling a volume approximately 1.5 feet high by 27 mats, each of which is substantially 18 square feet in area, utilizing approximately 1.75 cubic feet of solution. The total cubic volume being filled is then 1.5.times.27.times.18=729 cubic feet. Dividing this by 1.75 cubic feet gives an expansion ratio of 417 to 1. Japanese patent publication SHO 60-34901 has a similar disclosure and shows an expansion ratio of 150-500, preferably 200-400 liters per kilogram which is substantially the same per liter (liter per liter) as one kilogram of water occupies one liter in volume. The lowest expansion ratio shown, for a composition not of the invention, is less than 50 but is not otherwise specified. Japanese patent publication SHO 58-17161 is also of interest in this respect. The smallest expansion ratio (bubble multiplication) shown in the examples is 140 to 1.
Each of the aforementioned Japanese publications shows only the preparation of so-called dry foams and their application to relatively large crawl spaces. Dry foams do not carry enough pesticide to effectively control subsurface pests or to fertilize and/or otherwise alter the properties of soil. Thus, if they were to be injected beneath into the soil along with plowing, which is not contemplated by the publications and has not been attempted, they would not be capable of distributing throughout the soil an effective amount of 1) pesticide and thereby forming an effective pest barrier and/or 2) fertilizer or soil adjuvants to effectively alter the properties of the soil. Such foams would thus be highly unsuitable for and have not been utilized for the purpose of injection into the soil to control subsurface pests, etc.
British patent specification 1 274 442 is of interest in this area in that it shows the preparation of foams for being directly contacted with pests such as bacteria within closed containers or pipelines, apparently those associated with the food industry such as the milk and beer industries. Essentially, the containers or pipelines are filled with the foam which remains in place for a long enough time so that the pests can contact it directly and thereby be controlled. In the food industry, deposition of residual pesticides would be highly undesirable since contamination of the food (or drink) would almost certainly occur. Hence, British patent specification 1 274 442 is not concerned with foam deposition of residual pesticides, particularly not in soil or for the control of subsurface pests.
U.S. Pat. No. 4,822,613, issued Apr. 18, 1989 to A. Rodero discusses the preparation of pesticide containing highly stable water soluble foams which can be formed in situ utilizing a propellant, generally in a spray can type of arrangement. The patent discusses a foam which remains in place for a week or more. Control of pests is via direct contact with the foam which may be generated in place in a drain pipe. The foam can be washed away when it has done its job by flushing with water. This patent is also not concerned with depositing a pesticide in a soil to control subsurface pests.
It would be highly desirable if a method, an apparatus and/or a device were available for depositing a soil additive into soil to control subsurface pests in a manner such that the soil additive was very effectively and widely distributed throughout the soil while the amount of soil additive deposited was environmentally acceptable. The providing of such a device, apparatus and method constitutes the main objective of the present invention.